1. Field of the Invention
The invention relates to a video signal processing apparatus and a video signal transmitting method whereby a component video signal of a form of an analog signal can include additional information of a form of a digital signal, for example, copy control information.
2. Description of the Related Art
Hitherto, various systems for superimposing digital additional information to an analog video signal have been made. For example, in a character multiplex broadcasting, a character broadcasting signal constructed by characters, figures, additional sounds, and the like is multiplexed to a horizontal scanning period in which no video signal exists in a vertical blanking period of a normal television radio wave. In order to transmit picture recording information in an analog VCR (video cassette tape recorder), there has also been proposed a system in which a digital signal of 20 bits is inserted in a predetermined horizontal scanning period within a vertical blanking period of a video signal and copy management information and information such as a date of picture recording and the like are transmitted by the digital signal (called VBI data or a video-ID).
Further, in these days when a video signal of a high picture quality can be provided by not only a prerecorded tape (soft tape) but also a terminal of a digital broadcasting and a disk medium such as a DVD or the like, a limitation of a copy by the analog VCR becomes a serious subject in order to protect a copyright. As systems other than the above-mentioned VBI data, a pseudo sync signal adding system and a split burst system have also been proposed as copy limiting systems. The pseudo sync signal adding system is a system such that an amplitude of a predetermined horizontal sync pulse which is included in the vertical blanking period and is detected as a level of a video signal by an AGC circuit is set to be larger than the normal amplitude and, when the AGC is made operative, an amplitude of an analog video signal is reduced to a small value of a degree such that the amplitude of the signal cannot be reproduced. The split burst system is a system such that a split burst signal in which a phase of a color burst signal has partially been inverted is added to a part of one picture plane.
Each of the above-mentioned character multiplex broadcasting and the additional information transmitting method of the VBI data or the like is a system for superimposing data to a predetermined horizontal scanning period in the vertical blanking period of the composite video signal having a form of an analog signal. Therefore, in case of transmitting an analog component signal, for example, three primary color signals (called RGB signals), such a system cannot be used. For instance, as a video output of a personal computer, a form of the RGB signals is generally used, so that the conventional proposed additional information transmitting system cannot be applied. Accordingly, there is a problem such that when an NTSC signal is formed by supplying analog RGB signals outputted from the personal computer to an NTSC encoder, since copy control information is not added to the NTSC signal, the NTSC signal is recorded by the analog VCR, so that the copy prevention cannot be accomplished.